Mild hybrid vehicles often include a belt-driven starter generator (BSG) system that includes a motor generator unit (MGU) physically coupled to a crankshaft of an engine and electrically connected to a battery system of the vehicle. The BSG system controls the MGU to operate as either a torque generator (e.g., for starting or restarting the engine) or a torque consumer (e.g., to charge the battery system). When operating as a torque generator, the MGU is powered by electrical energy provided by the battery system to drive the crankshaft. When operating as a torque consumer, the MGU is powered by the crankshaft. One operating scenario where the BSG system typically operates the MGU as a torque consumer is a deceleration fuel shutoff (DFSO) event. During a DFSO event, a throttle valve of the engine is typically closed and engine pumping loss is near its maximum. By modifying engine operation to reduce pumping losses and using this pumping loss delta for electricity generation via the MGU, the vehicle performance remains the same while operation efficiency (e.g., fuel economy) is increased.
Due to various operational constraints (noise/vibration/harshness (NVH), emissions, etc.), however, modified engine operation to reduce pumping losses must be actively and tactically controlled. One method of reducing engine pumping losses is opening the throttle valve to improve engine breathing. The MGU, however, is only able to absorb a certain amount of the pumping loss reduction achievable by opening the throttle valve. A very complex, non-linear empirical approach involving many calibration tables based on dynamometer mapping is typically used to determine the desired pumping loss/throttle valve position. This approach, however, requires extensive calibration effort and memory storage for each application. Accordingly, while such mild hybrid vehicle control systems work well for their intended purpose, there remains a need for improvement in the relevant art.